From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56236 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Obh6p-0002oq-AR for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:45:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Obh6o-0002yW-3C for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:45:47 -0400 Received: from mail-gy0-f173.google.com ([209.85.160.173]:35215) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Obh6o-0002yO-0a for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:45:46 -0400 Received: by gyd10 with SMTP id 10so83757gyd.4 for ; Wed, 21 Jul 2010 14:45:45 -0700 (PDT) Message-ID: <4C476A8A.6000707@codemonkey.ws> Date: Wed, 21 Jul 2010 16:45:46 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help References: <4C4704FC020000480009AB6E@sinclair.provo.novell.com> <4C475EC0.2000805@codemonkey.ws> <20100721213238.GB28871@redhat.com> In-Reply-To: <20100721213238.GB28871@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: qemu-devel@nongnu.org, Bruce Rogers On 07/21/2010 04:32 PM, Daniel P. Berrange wrote: > On Wed, Jul 21, 2010 at 03:55:28PM -0500, Anthony Liguori wrote: > >> On 07/21/2010 03:32 PM, Bruce Rogers wrote: >> >>> Libvirt parses qemu help output to determine qemu features. In particular >>> it probes for the following: "cache=writethrough|writeback|none". The >>> addition of the unsafe cache mode was inserted within this string, as >>> opposed to being added to the end, which impacted libvirt's probe. >>> Unbreak libvirt by keeping the existing cache modes intact and add >>> unsafe to the end. >>> >>> This problem only manifests itself if a caching mode is explicitly >>> specified in the libvirt xml, in which case older syntax for caching is >>> passed to qemu, which it no longer understands. >>> >>> Signed-off-by: Bruce Rogers >>> >>> >> Errr, libvirt is still doing this? >> >> This comes up frequently and it's a real PITA. Help text is not a >> feature probing interface. This is a libvirt bug and it needs to be >> fixed in libvirt >> > Of course, there is no viable alternative yet. Yes there is. Use the version number. Regards, Anthony Liguori > The QMP patches I > sent a few weeks back now to add ability to query capabilities were > intended to provide the neccessary support in QEMU for us to use > instead of -help. Given that QMP isn't going to be declared stable > in 0.13 though, it looks like we'll be continuing to use -help > until the 0.14 release of QEMU. > > > Regards, > Daniel >